Production of copper containing



United States Patent ,"cc

PRODUCTION OF COPPER CONTAINING CATALYSTS Laurence Roy Pittweli and Richard John Young, Nortonon-Tees, England, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application May 12,1952,

Serial No. 287,418 Claims priority, application Great Britain June 6, 1951 9 Claims. (Cl. 252-454) posed to produce catalysts of these types containing copper or nickel as their active constiutents by treating cop per-silicon or nickel-silicon alloys with aqueous alkali.

In particular, it has been proposed to produce a copper silicon catalyst by the removal of up to 50% of the silicon from a copper-silicon alloy having a copperzsilicon weight ratio from 80:20 to 92:8 by treatment with an aqueous solution of sodium hydroxide or potassium hydroxidc of 15% to 50% concentration by weight.

We have now found that copper-silicon alloys having a specified alloy composition may be activated by treatment with steam or water at an elevated temperature.

Thus, according to the present invention, there is provided a process for the production of copper-containing catalysts, which comprises the step of treating a coppersilicon alloy, which is in granular or powdered form,

and which has a copper content of less than 87.5% by weight, with steam or water at a temperature in excess of 200 C., to remove or to convert to silica at least a part of the silicon content of the alloy.

The particle size of the alloy used for the production ofthe catalyst may vary widely. For example, particles grading between and 200 microns may be activated by the process of the present invention. Similarly, catalysts may be prepared from granules grading between hi and 1". The strength of the granules after activation depends upon the amount of silicon removed, or converted to silica. A high degree of silicon removal or, conversion to silica, results in the production of weak granules, which may break down, or be broken down, into an activated particulate catalyst.

Suitable alloys may be prepared by melting together copper and silicon in a graphite crucible in a furnace. The melt may be protected from the atmosphere by, for example, a layer of powdered charcoal. When the melt is homogeneous, it is chill-cast as thin slabs of /2" to thickness in heavy copper or steel tablet moulds. The cold product is crushed in a jaw crusher, and graded. It is desirable for the alloy, and also for the final catalyst, to be substantially free from .sulphur, arsenic, antimony, iron and halogens. It is preferable to employ alloys containing at least 50% by weight of copper, and,

more preferably, the alloys should have a copper content in the range of to by weight.

Prior to activation with steam or water at a temperature in excess of 200 C., the particles or granules of alloy may be treated with a solution of a caustic alkali, preferably a sodium hydroxide solution containing from 0 high activity. The conversion or removal of silicon in 2,734,873 a ed eb.

0.5 to 30% by weight NaOH, at a temperature of 20 to C. If desired, this treatment may be carried out;by contacting the alloy with a stream of caustic alkali, having a space velocity of, for example, up to 30 litres 5 .of sodium hydroxide per litre of alloy per hour. This has the effect of dissolving free silicon from the alloy. The term free silicon refers to that silicon which is present in the alloy .in excess of that present in the CusSi phase. The removal of this free silicon produces fissures in the alloy, which is then more readily activated by steam or water at a temperature in excess of 200 C.

The alloy is then activated bytreatment with steam or water at a tempeartureof at least 200 C. Preferably the activation is carried out at a temperature in the region of 300 C., and when thisis accomplished by the use of waterit is necessary towork at a pressure sufficiently elevated to maintain the water in the liquid state. in general, however, it is preferable to carry out the activation by the use of the steam, rather than water.

The amount of silicon removed from the granules or powder, or converted to silica, may be measured by the quantity of hydrogen produced, in accordance with the equation:

or by the;increas e inweight of the catalyst resultant upon the conversion of the silicon to silica. The conversion to silica or removal of, for example 40% of the silicon present in a copperzsilicon alloy containing 15% by weight of silicon, -gives rise to catalysts whichpossess a excess of this amount is not deleterious, and may result in the production of a catalyst of enhanced activity. The conversion-or removal of lesser. amounts of silicon also results in the production of active catalysts, but the activity maybe below the optimum value. The'conversion or removal of a major proportion of the silicon results in theproduction of a particulate catalyst, whereas activation involving a low degree of silicon conversion or removal enables the catalyst to retain its granular state.

After activation, the catalysts of the present invention, particularly if produced by treatment with steam, may contain silica, and, ifv desired, this may, be removed by treating. the catalystwith a caustic alkali, for example, sodium hydroxide. v

The final catalyst comprises active copper, together with, if desired, silica and an amount of silicon depend ing upon the composition of the original alloy, the duration of the activation, and the temperature at which this is carried out.

The catalysts produced by the process of the present invention may be employed in a wide range of reactions, such as, for example, the hydrogenation of unsaturated hydrocarbons and carbonyl compounds, such as aldehydes and ketones, the dehydrogenation of alcohols, and the reductive amination of carbonyl compounds, for example, the conversion of acetone to isopropylamine by the reaction:

The reactions as 'hereinbefore described may also be carried out with the powdered catalyst maintained in the fluidised state.

Reactions involving .the'presence of steam as a reactant or product result, when using a granular catalyst containing an. appreciable amount of silicon, in the further conversion of silicon to silica, and the consequent disintegration to particles ofthese granules. catalysts of this type should not be used in'such reactions 0 if the presenceinthe reactoror product of finely divided catalyst is undesirable.

As a result, granular It is a feature of the present invention that the activation process may be carried out simultaneously with the reaction in which the catalyst is employed. Thus, a mixture comprising ethylene, hydrogen and water vapour may be contacted with a copperzsilicon alloy at a temperature in excess of 200 C. The percentage of ethylene converted to ethane increases with operating time, corresponding to increasing catalyst activity, until the latter reaches its maximum value. In the same way, nitrobenzene may be converted to aniline, the catalyst being activated by the water liberated in the conversion.

Catalysts of the present invention are inoperative for the hydrogenation of aromatic nuclei, and they may therefore be used in selective hydrogenations, such as the hydrogenation of styrene to ethyl benzene.

Catalysts of the present invention lose their activity after prolonged use. They may be reactivated by treatment with oxygen or air at an elevated temperature, followed by reduction at elevated temperature, or by removing or converting to silica a further amount of silicon, if this is present in the deactivated catalyst, by treatment with steam or water at a temperature in excess of 200 C.

In the examples given below, the space velocity of sodium hydroxide is expressed as the number of litres of this passed per hour per litre of alloy. Similarly, in examples illustrating the use of the activated catalyst, the space velocities are expressd as litres of reactant passed per hour per litre of catalyst-filled space, the volume of the reactant being calculated at N. T. P.

Example 1 A copper-silicon alloy in the form of granules grading between A3" and A", and having a copper content of 85% by weight, was treated with steam at a temperature of 300 C. for 48 hours. The product was an aggregated mass of finely divided copper and silicon.

This catalyst was then employed for the hydrogenation of ethylene to ethane. An ethylene-hydrogen mixture was passed over the catalyst maintained at a temperature of 300 C., the ethylene having a space velocity of 400 and the hydrogen a space velocity of 8000. When operating under these conditions, 60% of the ethylene was converted to ethane.

Example 2 A copper-silicon alloy in the form of granules grading between /s" and A" and having a copper content of 85% by weight was treated at a space velocity of 30 with a 30% solution of sodium hydroxide at 98 C. for 40 hours, and then treated with steam at a temperature of 300 C. for 24 hours. The product was an aggregated mass of finely divided copper and silica.

This catalyst was then employed for the hydrogenation of ethylene to ethane. An ethylene-hydrogen mixture was passed over the catalyst maintained at a temperature of 300 C., the ethylene having a space velocity of 200 and the hydrogen a space velocity of 8000. When operating under these conditions, more than 85 of the ethylene was converted to ethane;

Example 3 A copper-silicon alloy as used in Example 2 was treated at a space velocity of 30 with an aqueous solution of sodium hydroxide containing 30% by weight NaOH, at a temperature of 98 C., to remove the silicon present in excess or that contained in the CusSi phase. This treatment was continued for 40 hours, and the product was then used for the hydrogenation of nitrobenzene; this was contacted with the catalyst at a liquid space velocity of 2 in the presence of hydrogen having a space velocity of 7000, the catalyst being maintained at a temperature of 300 C. Initially, the catalyst had an activity which was too small, to measure, but the activity increased with operating time, so that after operating for 20 hours, more than of the nitrobenzene was being converted to aniline.

A second sample of the copper-silicon alloywas treated, as described above, with sodium hydroxide, and then with steam for 24 hours at 300 C. On using this catalyst for the conversion of nitrobenzene to aniline, it was found that the catalyst had an initial activity equal to that attained after 20 hours by the catalyst which had not been steam activated.

This example illustrates the fact that a catalyst which is not initially activated by steam undergoes continuous activitation during use in a reaction in which steam is involved or liberated. The activity of a catalyst employed in this manner increases with time until a maximum activity is attained, after which the activity remains constant, or decreases slowly, possibly owing to carbon deposition on the catalyst surface. 7

Example 4 As described in Example 3, granules of a coppersilicon alloy containing by weight of copper and 15% by weight of silicon were treated witha 30% by weight solution of sodium hydroxide to remove from the alloy silicon in excess of that present in the CusSi phase. The product was then used for the hydrogenation of ethylene:

(a) Ethylene was passed at a space velocity of 400 over the catalyst maintained at a temperature of 300 C. Hydrogen was passed simultaneously through the reaction zone at a space velocity of 8000. In this experiment, the gases were thoroughly dried before being admitted to the reaction zone. The catalyst was initially inactive, and no increase in activity occurred after operating for 30 hours.

(b) The process described in (a) above was repeated except that moist ethylene and hydrogen were employed. The catalyst had no initial activity, but the activity increased with increasing operating time, until, after 20 hours running, 60% of the ethylene being introduced into the reaction zone was undergoing conversion to ethane.

In a control experiment, the granules, after treatment with sodium hydroxide as described above, were treated with steam at a temperature of 300 C. The product was then employed in the process described in (a) above. The initial activity of the treated alloy was such that 60% of the ethylene introduced into the reaction zone was converted to ethane. This activity was maintained throughout the course of operation for 50 hours.

Example 5 As described in Example 3, granules of a coppersilicon alloy were treated with sodium hydroxide to remove silicon in excess of that contained in the CuaSi phase. Samples of the alloy were then treated at 300 C.

.with steam for varying times, and the silica produced Residual silicon (percent of weight of alloy) Percent conversion of ethylene to ethane Duration of steam treatment (hours) These figures show that the catalyst activity is independent, under the conditions of operation, of the amount of residual silicon if this lies between 2.0% and 9.0% by weight.

We claim:

1. A process for the production of a copper-containing catalyst which comprises treating a copper-silicon alloy having a copper content of not less than about 50% by weight and not more than 87.5% by Weight with water at elevated pressure and at a temperature in excess of 200 C. to lower the content of elemental silicon present in the alloy by a substantial amount and suflicient to produce an activated catalyst.

2. A process for the production of a copper containing catalyst which comprises treating a copper-silicon alloy having a copper content of not less than about 50% by weight and not more than 87.5% by weight with steam at a temperature in excess of 200 C. to convert to silica a substantial amount of the elemental silicon present in the alloy, said amount converted being sufiicient to produce an activated catalyst.

3. A process for the production of a copper-containing catalyst which comprises treating a copper-silicon alloy having a copperzsilicon ratio of 70:30 to 85 :15 with water at elevated pressure and at a temperature in excess of 200 C. to lower the content of elemental silicon present in the alloy by at least 40% by Weight and sufiicient to produce an activated catalyst.

4. A process for the production of a copper-containing catalyst which comprises treating a copper-silicon alloy having a copperzsilicon ratio of 70:30 to 85:15 with steam at a temperature in excess of 200 C. to convert to silica at least 40% of the elemental silicon present in the alloy, said amount converted being sufficient to produce an activated catalyst.

5. A process for the production of a copper-containing catalyst from a copper-silicon alloy containing substantial amounts of free silicon which comprises treating said copper-silicon alloy having a copper content of not less than about 50% by Weight and not more than 87.5% by Weight with a solution of caustic alkali to remove the free silicon from the alloy, and treating the product with water at elevated pressure and at a temperature in excess of 200 C. to lower the content of elemental silicon present in the alloy by a substantial amount and sufiicient to produce an activated catalyst.

6. A process for the production of a copper-containing catalyst from a copper-silicon alloy containing substantial amounts of free silicon which comprises treating said copper-silicon alloy having a copper content of not less than by weight and not more than 87.5 by weight with a solution of caustic alkali to remove the free silicon from the alloy, and treating the product with steam at a temperature in excess of 200 C. to convert to silica a substantial amount of elemental silicon present in the alloy, said amount converted being sufiicient to produce an activated catalyst.

7. A process for the production of a copper-containing catalyst from a copper-silicon alloy which comprises treating said copper-silicon alloy having a copper content of not less than about 50% by weight and not more than 87.5% by weight with steam at a temperature in excess of 200 C. to convert to silica a substantial amount of elemental silicon present in the alloy and thereafter removing at least a part of the silica produced by treatment with a caustic alkali.

8. A process for the production of a copper-containing catalyst which comprises treating a copper-silicon alloy having a copper content of not less than about 50% by weight and not more than 87.5% by Weight with steam at a temperature in excess of 200 C. to convert to silica substantially all of the elemental silicon present in the alloy, and thereby producing an activated catalyst.

9. A process for the production of a copper-containing catalyst from. a copper-silicon alloy containing substantial amounts of free silicon which comprises treating said copper-silicon alloy having a copper content of not less than about 50% by weight and not more than 87.5% by weight with a solution of caustic alkali to remove the free silicon from the alloy, treating the product with steam at a temperature in excess of 200 C. to convert to silica a substantial amount of elemental silicon present in the alloy, and thereafter removing at least a part of the silica produced by treatment with a caustic alkali.

References Cited in the file of this patent UNITED STATES PATENTS 1,447,557 Legg Mar. 6, 1923 1,456,969 Brown et al May 29, 1923 2,380,997 Patnode Aug. 7, 1945 2,466,412 Gilliam et a1. Apr. 5, 1949 2,606,142 Storch et al. Aug. 5, 1952 

1. A PROCESS FOR THE PRODUCTION OF A COPPER-CONTAINING CATALYST WHICH COMPRISES TREATING A COOPER-SILICON ALLOY HAVING A COPPER CONTENT OF NOT LESS THAN ABOUT 50% BY WEIGHT AND NOT MORE THAN 87.5% BY WEIGHT WITH WATER AT ELEVATED PRESSURE AND AT A TEMPERATURE IN EXCESS OF 200* C. TO LOWER THE CONTENT OF ELEMENT SILICON PRESENT IN THE ALLOY BY A SUBSTANTIAL AMOUNT AND SUFFICIENT TO PRODUCE AN ACTIVATED CATALYST. 